1. Field of the Invention
The present invention relates to solid-state image pickup devices and electronic apparatuses. In particular, the present invention relates to a solid-state image pickup device including pixels having photodiodes on a light-incident surface, the pixels being arranged in a matrix, and relates to an electronic apparatus including the solid-state image pickup device.
2. Description of the Related Art
In solid-state image pickup devices such as complementary metal oxide semiconductor (CMOS) sensors and charge-coupled devices (CCDs), light is incident on photodiodes (photoelectric conversion units) arranged on surfaces of semiconductor substrates to generate signal charges in the photodiodes, resulting in image signals.
In CMOS sensors, for example, photodiodes are provided in respective pixels arranged in a two-dimensional matrix on a light-incident surface. Signal charges generated and accumulated in photodiodes in receiving light are transferred to floating diffusion by driving CMOS circuits. Signal charges are converted into signal voltages and read out.
In charge-coupled devices, for example, photodiodes are provided in respective pixels arranged in a two-dimensional matrix on a light-incident surface similar to CMOS sensors. Signal charges generated and accumulated in photodiodes in receiving light are transferred by vertical and horizontal transfer channels and read out.
Solid-state image pickup devices such as CMOS sensors include, for example, photodiodes formed on surfaces of semiconductor substrates. Insulating films composed of, for example, silicon oxide, are formed on photodiodes. Insulating films include wirings formed in regions except photodiode regions so as not to preclude the incidence of light on photodiodes.
In such solid-state image pickup devices as described above, however, the miniaturization of devices results in a reduction in area of light-incident surfaces, disadvantageously reducing the proportion of incident light and sensitivity characteristics.
As measures to overcome the disadvantages, a structure in which concentration of light is performed with on-chip lenses and/or intralayer lenses have been developed. In particular, a solid-state image pickup device including optical waveguides arranged in an insulating film above photodiodes and configured to guide light incident from the outside to a photodiode has been developed.
Solid-state image pickup devices disclosed in Japanese Unexamined Patent Application Publication Nos. 2003-324189 and 2004-207433 each have a structure described below.
The solid-state image pickup device includes a photodiode formed in a pixel arranged in a matrix on a substrate, an insulating film covering the photodiode, a trench in the insulating film above the photodiode, and an optical waveguide in the trench.
In the solid-state image pickup device described above, a copper wiring formed by a damascene process is embedded in the insulating film. The insulating film includes a diffusion preventing film for copper constituting the copper wiring and an etching stopper film used in forming the trench.
In Japanese Unexamined Patent Application Publication Nos. 2003-324189 and 2004-207433, the optical waveguide is formed so as to pass through the diffusion preventing film and the etching stopper film. It is known that in such a structure, dark current and bright defects, which are representative characteristics of solid-state image pickup devices, are unsatisfactory.
Japanese Unexamined Patent Application Publication No. 2006-339339 discloses a solid-state image pickup device including an optical waveguide having the same structure as above.
In the solid-state image pickup device disclosed in Japanese Unexamined Patent Application Publication No. 2006-339339, the optical waveguide is formed so as to reach a silicon nitride film that covers a surface of a substrate.
Japanese Unexamined Patent Application Publication No. 2006-190891 discloses a solid-state image pickup device including an optical waveguide having the same structure as above.
In the solid-state image pickup device disclosed in Japanese Unexamined Patent Application Publication No. 2006-190891, the optical waveguide is formed so as to reach a diffusion preventing film formed in a layer having a wiring formed by a dual damascene process.
In Japanese Unexamined Patent Application Publication Nos. 2006-339339 and 2006-190891, the optical waveguides are formed so as not to pass through the silicon nitride film and the diffusion preventing film that cover the substrate surface, thereby improving the characteristics of dark current and bright defects compared with the solid-state image pickup devices disclosed in Japanese Unexamined Patent Application Publication Nos. 2003-324189 and 2004-207433.